Canadian Fire Alarm Association –The Journal February 2012
TWO-STAGE FIRE ALARM SYSTEMS
By D. Goodyear
It is known that a well-designed fire alarm system is essential for life safety in a building. It is also known within the fire alarm community that the Building Code describes what types of fire alarm operation are permitted in a building based on the occupancy and use of the building. When a two-stage fire alarm system is considered for installation in a building, there are some significant life safety implications that should be addressed by a number of people with converging and vested interests: the fire alarm sales person, the fire alarm designer, the engineer, the architect, the authority having jurisdiction, the property owner and manager, and the fire alarm technician.
A two-stage fire alarm system can provide superior protection but a two-stage fire alarm system design that is only based on the Building Code, the fire alarm installation standard CAN/ULC S524 or a fire alarm manufacturer’s specifications, will inevitably not provide the best protection for the occupants.
Since a two-stage system does not immediately cause evacuation of all occupants, they are potentially at a greater risk because we know that fires can develop to a lethal level within minutes. Caution, therefore, is advised when dealing with a two-stage fire alarm system: know the implications.
This article will outline how the various two-stage systems operate and what the implications are.
Within the two-stage system category there are two basic variations: institutional types and those for all other buildings.
TWO STAGE SYSTEMS IN INSTITUTIONS
Historically, two-stage systems have been and continue to be used in institutions such as hospitals and health care facilities where immediate evacuation of the occupants is neither desired nor practical. In this scenario the fire detection devices cause the fire alarm panel to send signals to the fire department or monitoring station (fire alarm receiving center) and operate the ancillary functions. Alarm signals to evacuate occupants do not sound.
The fire alarm system only sounds an alert signal, (perhaps a chime sound) to notify trained staff on duty to carry out their duties under the established fire procedures. There is no prescribed sound for the alert signal to notify staff but it must be distinctly different from the evacuation (alarm) signal. In new buildings, that evacuation signal will be the temporal signal.
There is a key-switch in each manual station that when operated will activate the evacuation or the “second stage”. Trained staff have the keys for the manual stations to initiate the second stage.
It is crucial to recognize that it is the trained staff who are responsible for evacuating the building occupants and that human interaction is an integral part of the fire protection system.
IMPLICATIONS
It is evident that the two-stage system has serious implications:
- The Fire Safety Plan requires much greater detail,
- Significant training is implied,
- Staff levels must be considered.
And there are issues such as:
- Who has the evacuation keys?
- Where are the keys located?
- Who makes the evacuation decision?
- Under what conditions is evacuation mandatory?
Most institutional buildings will also have voice communication (paging) systems and these must be used to co-ordinate aspects of the fire safety procedures. This is a minefield that must be navigated. The concept of how the Fire Safety Plan is to be managed and integrated with the fire alarm system must be established before the equipment is programmed and installed.
VARIATIONS OF MODIFIED TWO-STAGE SYSTEMS
When a two-stage system is installed in buildings other than institutional buildings, the two-stage operation is sometimes referred to as a modified two-stage or zoned two-stage fire alarm system. Modified two-stage system installations are found in large office complexes, large residential complexes, hotels, shopping malls and other buildings where immediate evacuation of all the occupants is not desired.
In this configuration, if an alarm occurs by the actuation of any input device, the alarm signals sound (the evacuation signal) in the area or zone where the device was activated. Alert signals sound in all other areas of the building to notify supervisory staff of the alarm condition and signal them to undertake their duties as required in the Fire Safety Plan.
Many systems incorporate another version of a modified two-stage system. The alarm signals occur not only in the initiating zone but the adjacent zone most endangered, typically the floor above and also the floor below, which in many cases is the floor where the fire department would respond to and set up their staging area to tackle the fire. This configuration of providing alarms on the initiating floor, the floor above and the floor below may not apply in all buildings or in all areas of buildings (such as the lower floors of a building or a complex). The configuration is altered, for instance, in a parking garage where all of the floors below grade may be evacuated at one time.
IMPLICATIONS
There is a minefield of implications since the modified two-stage fire alarm system does not cause immediate evacuation of all the occupants. These systems are reliant on supervisory staff.
In addition to programming and zoning the fire alarm control panel signalling, it is important to note that in non-institutional buildings, two-stage fire alarm systems are required to have a five-minute failsafe timer. If the supervisory staff do not respond and acknowledge the alarm at the response center (the fire alarm control panel or Central Alarm and Control Facility) the fire alarm system will sound full evacuation within five minutes. From a fire safety view, that five minutes may be critical because fires can potentially develop to a lethal level within minutes. This is a crucial consideration that cannot be overlooked.
How is the Fire Safety Plan structured to permit staff to evaluate a possible fire situation and immediately initiate evacuation if necessary?
There are still many of the same serious implications that are inherent in institutional buildings with two-stage systems. It should also be remembered that in most buildings the elevators will be recalled and returned to ground level and will be out of service. The use of elevators would not be recommended in any case.
In most situations there should be at least two staff on duty: one to evaluate the possible fire condition in the area of the building where the alarm was initiated and one person at the control panel. In many buildings that have a two-stage fire alarm system, there may not be two staff members on duty 24/7. On nights and weekends, however, there may be people working late or cleaning staff in the building and these persons could be at risk in the event of a fire. Does the fire alarm system correlate with how the building is managed?
TWO-STAGE SYSTEMS and THE FIRE SAFETY PLAN
The sequence of operation of a fire alarm system, the Fire Safety Plan and well-trained staff are interdependent ingredients. Unfortunately, in many instances the equipment design decisions and sometimes the installation are completed before the Fire Safety Plan concept has been fully developed and there is little input on how the building is managed and staffed.
Two-stage systems, institutional types or the modified two-stage, are frequently very complex and have a multitude of additional considerations because there is no immediate evacuation of all the occupants.
The design concept and equipment of two-stage systems can provide anything from just adequate to superior life safety systems. It would be disastrous, however, if the design of a building that incorporated a two-stage fire alarm system failed to consider the key elements of the Fire Safety Plan. Fire protection systems are dependent on: reliable equipment, accurate fire alarm programming, human intervention, trained staff familiar with their duties under the Fire Safety Plan and how the building is managed.
THE FIRE ALARM TECHNICIAN
This article has discussed two-stage systems and the significant concerns that should not be overlooked by fire alarm designers and the authority having jurisdiction examining the project plans. But there’s also an aspect for the fire alarm technician to consider before stepping into the minefield.
The fire alarm technician should not only be familiar with two-stage sequence of operation for the particular panel but also with the critical elements of the building Fire Safety Plan. By nature when the fire alarm technician, a human element, works on a system, he or she has altered the normal plan. The technician should discuss his or her responsibilities with building supervisory staff so that in the event of a fire, staff responsible under the Fire Safety Plan are informed and know what alternate action to take. The technician should ensure that there is a procedure that will be followed if a fire occurs during servicing the panel or if an alarm is received from an area of the building that is not under test. The following questions concerning what happens in the event of a fire should be addressed:
- How will the building supervisory staff be notified?
- How will the monitoring company or fire department be notified when part of the building fire alarm is bypassed, out of service or under test?
CONCLUSION
There are implications when a two-stage fire alarm system is installed in a building. In order to obtain the best fire protection system for the occupants, it is essential when considering a two-stage system that the system be coordinated with an effective Fire Safety Plan and that it reflects how the building staff are trained and how the building is managed.